Unvented System / Pumps / accumulator or mainsboost

Discussion in 'Plumbers' Talk' started by vaderag, Jun 10, 2021.

  1. vaderag

    vaderag Member

    Long story short, as I understand it we have reasonabl(ish) pressure (we're in victorian house in Greater London) but relatively low flow rate and that means that firstly, shower flow/pressure is not great as standard but if toilet / tap is turned on it slows to a crawl

    We were due to have an accumulator installed today but due to the plumber mis-measuring on his initial inspection it was called off and need to look at other options as it looks like we're not going to get the accumulator where we wanted under the stairs.

    Every time i revisit my searches on this I get confused as to what is possible and what isn't, but would like to know what's available to me.

    It seems I could solve the pressure/flow on the shower with a pump, but then I see that pumps aren't allowed in unvented? But then not sure what would happen to the pump if the flow dropped anyway... So a bit confused...

    Anyone lend some insight? Is the accumulator the right way to go? Should I look at pumps? Am I missing something entirely?

    (Nb. Unvented tank is in the loft with the boiler, is more room up there if needed)

  2. jonathanc

    jonathanc Screwfix Select

    Shower pumps don’t work on unvented. You can have a mild booster pump on the mains flow but the best thing is a break tank and pump: I use a grundfos home booster which is combined tank and booster: should go under the stairs. If you really want you could leave things like dishwashers, washing machines and bogs on the direct mains abs just use the pumped supply for everything else
  3. just pumps

    just pumps Screwfix Select

    Have you seen or fitted the DAB version. Asking as I hear good things about them.
  4. vaderag

    vaderag Member

    So would that just go in line with the mains inlet after the stopcock?
    How loud is it? I've been really against the idea of a pump as I don't want a constant noise/hum

    Also, what is the pro/con/difference between this and an accumulator tank?
    It seems like the accumulator (mainsboost) would do the same job but without a pump?
  5. BillyBobToo

    BillyBobToo Active Member

    I fitted one for a friend at the end of 2019, along with an UHW cylinder. He is very pleased with it. You can hardly hear it when standing right beside it. Inverter controlled motor adjust to demand.
    just pumps likes this.
  6. vaderag

    vaderag Member

    Do you have a comparison of the DAB one vs the Grundfos? Would you say you would hear in the room below if it were fitted in the loft?

    Also just want to re-ask my question above
    what is the pro/con/difference between this and an accumulator tank?
    It seems like the accumulator (mainsboost) would do the same job but without a pump?
  7. BillyBobToo

    BillyBobToo Active Member

    An accumulator cannot give more than it gets. To increase the pressure you need a pump.
    You could try one of these: https://www.completepumpsupplies.co...md9HVFSgFY_ruFrsEP6vHzy1y_ALLR4xoCwQEQAvD_BwE
    I fitted one for a friend about 5 years ago and he has been very pleased with it.
    As always, check your requirements against the specs. Incoming mains flow has to be considered as to whether it will keep up with demand.
  8. vaderag

    vaderag Member

    So I had Stuart Turner around a while back and they told me to go for their mainsboost - they measured the flow and pressure and concluded that. That's kinda what got me onto the accumulator. But showers could use a little more oomph and if the accumulator isn't going to 'add' anything then I think it may not be sufficient? (I think it would add a bit if it were on ground level as will be losing on the way to the loft at the minute)

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